Device for hidden explosive mines



Aug. 31, 1948. R. c. DARNELL 2,448,020

DEVICE FOR HIDDEN EXPLOSIVE MINES filed May 17, 1943- gvwmvtom Richard E.Darne11 my mu l 32 35 tam wax-W tented Aug. 31,

DEVICE FOR. DEN EOSIVE MINES Richard C. Darnell, Champaign, Ill. -Jlipplicatlon May 17, 1943, Serial No. 487,295

2 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to explosive mines of the type which are hidden from view, usually by being buried in the ground, and provided with means which will cause the mine to explode when an object comes within the range of its eii'ectiveness. Detectors have been developed for seeklog out or locating such hidden mines, so that they may be safely destroyed. Such mine detectors usually operate with electromagnetic waves and are implemented with an exploring loop which is traversed over the ground, a deflecting needle or the like indicating the presence of the hidden metallic body; electromagnetic detectors are eflective to locate non-magnetic as well as magnetic mines provided they contain metal parts.

The object of this invention is to devise a means which will thwart and deter the electromagnetic detection 01' hidden mines by causing the explosion of the mine, and the destruction of the exploring party and the detector. when it comes within the electromagnetic field of the exploring loop of the detector. The invention is particularly designed for anti-tank mines the primer of which is fired when the large mass of. the tank comes within its range of efiectiveness, but will not be fired when the mine is approached by bodies or bodies containing no large mass of material. Hence anti-tank mines will not explode when approached by exploring parties or by the exploring loop of the detector or the detector box itself. The specific object of this invention is to devise a means for exploding an antitank mine or mines when approached, not only by a tank but by the exploring loop of a detector seeking to locate the mine. It is the purpose of the invention to sow a small number of such explosive devices among the standard anti-tank mines, so as to deter or discourage the attempts to locate the hidden anti-tank mines.

For the attainment of these and such other objects as may herein appear or be pointed out I have shown a number of embodiments of my invention in the accompanying drawing, wherein:

(Granted under the act oi March 8, 1883, as amended April 30, 1928; 370 0. G. 757) Fig. l is an electrical diagram illustrating one type of device having an A. C. relay;

Fig. 2 is an electrical diagram illustrating a second type of device differing from that of Fig. 1 in the provision of a D. C. relay;

Fig. 3 is an, electrical diagram illustrating a device having a grid glow tube relay; and

Fig. 4 is an electrical diagram of a circuitsimilar to that of Fig. 3, but including a condenser and inductance coil for tuning.

The explosive device of the character indicated above must be simple, compact, inexpensive. foolproof, and certain of action. If incorporating batteries the drain must be so small as to permit a continued life of several months. I have found that these conditions are met by the use of a simple pickup loop or antenna, such as designated ill in Fig. 1 in circuit with an A. C. relay H. The armature l2 of the relay is in a second circuit which includes a dry cell or battery l3 and the coil it of the primer or firing mechanism of the explosive device III. A. C. relays are generally less sensitive than D. C. relays; an arrangement employing a D. C. relay is shown in Fig. 2, wherein the relay 2| is in circuit with loop 20 and a rectifier 25, which is preferably of the dry type such as a selenium or copper oxide rectifier. The armature 22 of the D. C. relay is in circuit with battery 23 and the coil 24 of the primer or firing mechanism of the device 20. In both the circuit of Fig. 1 containing an A. C. relay and the circuit of Fig. 2 containing a D. C. relay, the loop picks up the electromagnetic field of the detector, the loop current energizing the relay to close the circuit to the primer.

In Fig. 3 is shown a circuit embodying a grid glow tube 39 of the gas filled type, the circuit of grid 3| being inductively coupled with loop 3t and battery or dry cells 32; the plate 33 of the tube is in circuit with coil 3% of the firing or primer mechanism of the device 30' and a second battery 35. The filament 36 is connected at the juncture of the grid and the plate circuits, as shown in the figure. To increase the sensitivity of the device a coupling or step-up transformer Mi may be interposed between the loop 30 and the grid 3! of the tube 39. Inasmuch as the'drain on the batteries must be small so as to permit a continued life of several months, vacuum tubes having heated filaments could not be used. The grid glow tube, however, is a cold cathode tube in which there is no battery drain until the tube is triggered by change in grid voltage. The batteries provide proper plate and grid potential until such time as the potential or the grid is changed as by the induction of a feeble voltage in the loop circuit caused by the electromagnetic waves of a detector. Thereat the change in grid potential triggers the tube to cause a flow of current in the plate circuit and through the coil M of the primer to explode the device and/or the anti-tank mine with which it is associated.

I 3 Whereas a thermionic tube having a grid central is shown in the drawinss it is clear that other gas-tilled tubes having either a controlled arid or controlled electrodes and using a cold cathode. may be employed. One example of the controlled electrode type' or tube is the "double gap" Western Electric tube (313C) To provide a safeguard against premature firing due to malfunction while being placed in service, a time delay switch ll may he placed in the plate circuit. The time delay mechanism may involve the use or a mechanical or electrical clockwork, or may be based on chemical pneumatic or other action. eriectlve to delay the closing of the circuit for several minutes or hours after removing an arming pull pin or other inaugurating means (not shown) Fig. 4 is similar to P13. 3 except that a condenser II and an inductance coil 31 are included in the loop circuit so as to tune or adjust the circuit to be in resonance with any predetermined frequency or hand of frequencies of the electromagnetic detector.

I claim: s

1. A device of the character described comprising. in combination, an explosive device for deterring the exploring oi hidden mines by electromagnetic detectors, adapted to be placed in hidden association with the said mines, an antenna in which a voltage is induced by the electromagnetic ileld of an approaching detector, 9. self-con- 5 the 0011 of which is in circuit with the said second source of current and the cathode oi said controlledglow tube.

2. The combination according to "claim 1 in which the first said circuit is iurther provided with an inductive coil and a condenser for tunin the said circuit to a predetermined frequency.

. CHARD ARNELI...

m c. p

BEFEBENCES CITED The following references are oi record in the file of this patent:

UNITED STATES PATENTS Number Name Date- 850,972 Schneider Apr. 23, 1907 2,212,986 Homi Aug. 2'7, 1940 s 2,379,447 Lindsey July 3, 1945 2,404,553 -Wales July 23,. 1946 FOREIGN PATENTS Number Country Date 163,758 Switzerland NOV. 1, 1933 521,339 Great Britain May 20, 1940 803,907 France L. '.....a-- July 20, 1936 

